Materials and Components – Section 2

Materials and Components – Section 2

1.  In crystalline solids, atoms are stacked in a regular manner.
A. True
B. False

Answer: Option A

2.  The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called
A. Weiss temperature
B. Curie temperature
C. Neel temperature
D. None of the above

Answer: Option C

3.  In metals, the average drift velocity of electron per unit field is called mobility.
A. True
B. False

Answer: Option A

4.  Ferrites have
A. a low copper loss
B. low eddy current loss
C. low resistivity
D. higher specific gravity compared to iron

Answer: Option B

5.  In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.
A. True
B. False

Answer: Option A

6.  When a material becomes a superconductor, its resistivity becomes
A. very small
B. zero
C. about 10% of normal value
D. about 20% of normal value

Answer: Option B

Explanation:

A superconductor has zero resistance.

7.  In a piezoelectric crystal, the application of mechanical force will cause
A. plastic deformation of crystal
B. magnetic dipoles in the crystal
C. electrical polarization in the crystal
D. shift in Fermi level

Answer: Option B

Explanation:

Piezoelectric materials permit conversion of mechanical force into electrical energy.

8.  Consider the following statement
If an electric field is applied to an n type semiconductor bar, the electrons and holes move in opposite directions due to their opposite charges. The net currents is

  1. both due to electrons and holes with electrons as majority carriers
  2. sum of hole and electron currents
  3. difference between electron and hole currents.

Which of above statements are correct?

A. 1 only
B. 1 and 2
C. 2 only
D. 3 only

Answer: Option B

Explanation:

The net current is sum of currents due to holes and electrons.

In n type materials, electrons are majority carriers.

9.  As the temperature of a pure silicon specimen is increased
A. the number of free electrons increases
B. the number of holes decreases
C. the number of holes increases
D. the number of free electrons and holes increases

Answer: Option D

10.  Assertion (A): In many materials, dielectric polarization causes mechanical distortion.

Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

Answer: Option C

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